PARIS — French authorities opened a terror investigation Tuesday after police shot and wounded a hammer-wielding man who yelled "This is for Syria!" as he attacked a Parisian police officer outside the historic Notre Dame Cathedral.

Some 600 people were inside the famous 12th century church while the drama was happening outside and within minutes one of Paris' most visited tourist destinations was swarming with heavily armed police officers.

The suspect is believed to be an Algerian student, based on the ID card found on him, and appears to have acted alone, French Interior Minister Gerard Collomb said. He was armed with kitchen knives as well as the hammer and yelled "This is for Syria!" when he struck.

"We've gone from sophisticated terrorism to terrorism where any tool will do," Collomb said.

The police officer was not seriously hurt, the minister said. The alleged attacker was rushed to a nearby hospital and his condition was not immediately known.

Collomb said that in the wake of this attack French authorities will hold a special meeting on Wednesday where they will reevaluate the state of emergency and other anti-terrorism measures.

Meanwhile, the U.S. Embassy in Paris urged Americans to steer clear of Notre Dame and the surrounding areas until police complete their investigation.

In the U.S., Senator Angus King (I-Maine) told MSNBC this appeared to be a "lone wolf" attack.

"These are the kind of attacks that are, that give everybody nightmares, because there’s no plot," he said. "There’s nothing that you can intercept."